Re: When is long enough to long?
The body is a machine, and eventually they will all wear out. But the mental and spiritual training can be continued until they pile the dirt on you. I've been told that those aspects and dimensions can actually become more acute to compensate as the body ages, kind of like what happens to one's senses of smell and hearing if the sense of sight is reduced or lost. I don't know how much truth there is to that, but it will be interesting to find out as I age.
I wish I could say that all instructors were giving the non-technical aspects their just deserves, but it does concern me that many younger students do not get the exposure to the mental or spiritual agenda that will help them continue training along those lines as they get older. There seem to be many who complain "I can't do this and that anymore... NOW what do I do?"
Another thing that doesn't have to slow down is one's ability to teach, and otherwise help others along the path.